Machines and methods for the forming, filling and sealing of packages made from a web or film or material are known in the art. These machines typically comprise a supply of package film, a former for forming the film into a continuous tube over a hollow, cylindrical mandrel, a device for feeding lengths of the film through the machine, and reciprocating stripping, sealing and cutting jaws for sealing and cutting the tube into a consecutive series of filled packages.
It is also known to use packaging film having preprinted marks on the film at each package length, and use a photocell control responsive to the preprinted marks to control the length of packaging film being fed.
In one known packaging machine, the film is fed from a driven roll of film through sealing and cut-off jaws. A photocell senses a preprinted mark on the package film being fed from the film roll to the sealing and cut-off jaws, and, working through a control device, thereupon brakes the drive and actuates the sealing and cut-off jaws. After a timed interval the film brake is released to resume the feeding of another length of package film until the photocell senses another preprinted mark on the film being fed and again brakes the film and actuates the sealing and cut-off jaws.
Another known packaging machine has a photocell and photoregistration control circuit which reads preprinted marks along the length of the package film. With the film being fed through the machine, when a preprinted mark is sensed by the photocell, the photoregistration control circuit signals a timer. Upon timing out, the timer actuates a brake of the film feeder device and actuates a second timer controlling the operation of a package sealer and cut-off device. After the second timer has timed out, the brake of the film feeder device is released and the package film is again fed until the next mark is sensed and the above sequence is repeated.
Yet another known packaging machine uses a clutch/brake unit operated by a programmable controller, and connected to an operating motor to drive a roll of package film to feed a length of package film through a package film sealing member. The packaging film has registration marks at package length intervals. The clutch remains activated providing for driving the roll of package film and feeding a length of package film until an optical scanner detects the passing of a registration mark on the package film and sends a signal to the programmable controller which disengages the clutch and engages the brake to stop the feeding of the package film. After a timed period sufficient to provide for the filling, sealing and cut-off of a package, the clutch is re-engaged and the brake disengaged thereby feeding another length of package film.
However, in these prior known machines difficulties arise in maintaining the lengths of package film being fed at exact dimentions, particularly as the package film may shrink or be stretched as it is being fed through these machines. Also because of high acceleration/deceleration forces, the belt wear that is experienced is unusually high. Also, these unusualy high forces actually limit the film types and the gauges of film that can successfully be used.